The neurobiological dimension of sexual orientation

158

“Sexual orientation is not a matter of choice, it is primarily neurobiological at birth”, Jerome Goldstein, director of the San Francisco Clinical Research Center, USA, stated at the 21st Meeting of the European Neurological Society (ENS) in Lisbon. “There are undeniable links. We want to make them visible to the eye” At the congress he showed how the brains of people of different sexual orientations – gay, straight, bisexual – work in different ways, applying volumetric magnetic resonance imaging (MRI), functional fMRI scanning, and PET scanning.

There have been several reports of twin studies indicating the probable genetic link of sexual orientation.Goldstein has begun accumulating a database of identical twins, whose sexual orientation will be further evaluated by MRI, fMRI scanning, and PET scanning.


“Using volumetric studies, there have been findings of significant cerebral amygdala size differences between homosexual and heterosexual subjects. Sex dimorphic connections were found among homosexual participants in these studies,” Goldstein noted. He provided current data regarding homosexuality showing differences and/or similarities, between the brains of homosexuals and heterosexuals.


Similarities between the brains of gay men and heterosexual women


“Some of the most striking results were delivered recently by Ivanka Savic-Berglund and Per Lindström of the Karolinska Institute, Stockholm, Sweden”, Goldstein reported. The Swedish experts performed volumetric studies, fMRI and PET measurements of cerebral blood flow. Using volumetric studies, they found significant cerebral and amygdala size differences between homosexual and heterosexual subjects. Thus the brains of homosexual men resemble those of heterosexual women and those of homosexual women resemble to heterosexual men. The plan for continued studies is to expand the number of subjects evaluated, thus verifying the validity of data already available.


Pheromonal studies also have added to the scientific knowledge of sexuality, according to Goldstein. “Sex-atypical connections were found among homosexual participants. Amygdala connectivity differences were found to be statistically significant and provided evidence towards sexual dimorphism between heterosexual and homosexual subjects.”


“We must continue to bring forward data that show the differences or similarities between the brains of homosexuals, heterosexuals, bisexuals, and trans-gender persons. Clearly the basis of sexual orientation is in the brain and differences in brain structure and function and the province of neurology,” Goldstein added. “Neuroscience has much to offer in the area of understanding the origins of all variations of sexual orientation. The neurobiology of sexual orientation and the gay brain, matched with other hormonal, genetic, and structural studies, has far-reaching consequences beyond sexual orientation.”


Treatment variations are already emerging as a result of recognition of sexual orientation differences and the advent of gender specific medicine.